Contents

Overview

The Paraflasher (Parallel Port Flasher) is low-cost simple flash programming device. It can be used to flash a variety of LPC flash chips and firmware hubs (FWH). The hope is someday it will also be able to support SPI chips. It is also meant to be modular so you can flash a variety flash chip packages. The Paraflasher is based on an old LPC programmer built to flash LPC chips on the xbox, the LPC^2 (Low Parts Count LPC Programming Cable). The Paraflasher is not for sale, it is meant for that "do-it-yourself" kind of person. Although if the project becomes popular, bare PCB's could be produced and sold at cost. Anyone with novice to moderate soldering skills can build one.

The Circuit Explained

Data Circuit

SN74CBTD3861

The Paraflasher is connected to the PC’s Parallel port via a DB25 Parallel extension cable and is run in SPP mode. The 10-Bit FET Bus Switch With Level Shifting is connected to data lines D0 – D6 convert the data signals from 5V to 3.3V needed by most if not all flash chips. The parallel port data lines D0, D1, and D2 are used for driving the control signals LCLK, LFRAME, and RST. The parallel port data lines D3, D4, D5, and D6 are used for bi-directional data transfers of the corresponding LAD0, LAD1, LAD2, and LAD3 lines. LAD0, LAD1, LAD2, and LAD3 lines are also buffered and feed back to the parallel port /Error, /SELIN, /PE, and /Ack signals. The 74HC244 is an advanced high-speed CMOS Octal Bus Buffer that acts as a simple signal buffer between D0, D1, /Error, /SELIN, /PE, /Ack and the LCLK, LFRAME, LAD0, LAD1, LAD2, LAD3 lines.

M74HC244B1R

Signals Simplified

Parallel Port

To LPC Signal

To FWH Signal

D0

LCLK

CLK

D1

LFRAME

FWH4

D2

RST

RP

D3

LAD0

FWH0

D4

LAD1

FWH1

D5

LAD2

FWH2

D6

LAD3

FWH3

/Error

LAD0

FWH0

/SELIN

LAD1

FWH1

/PE

LAD2

FWH2

/Ack

LAD3

FWH3

Power Circuit

I did not like the original power circuit design of using a wall-wart type power supply and a LED as voltage regulator, so I came up with the following and it works pretty slick. The Paraflasher is powered by USB via a USB printer cable. The jack is a USB type B. All of the grounds from every component requiring a ground is connected together. The +5 VDC from USB is connected to a PTC Resettable Fuse with trip current of 0.5 Amp (500mA). USB v2.0 specifies a maximum of 500mA so this will protect the PC’s USB port from any damage caused by short circuits, etc. If the PTC Resettable Fuse is tripped, disconnect the power source (USB), figure out what tripped the fuse and fix it, and wait a few seconds for the PTC Resettable Fuse to cool down and reset. Next I put in a simple LED circuit just for user aesthetics, so you know your getting power from USB. If you want to use a different color LED or if the blue LED is too bright you can adjust the ohms of the resistor. A 5V power line branches off from here and continues to the header to power a 5V flash chip. I went with the LM1084IT-3.3 voltage regulator because it is designed to convert 5V to a fixed output of 3.3V to power the octal buffer and a 3.3V flash chip. Simple and effective. National Semiconductor recommends for a 5V to 3.3V conversion to place a 10 UF Tantalum capacitor on both the input and output lines of the voltage regulator. They recommend using Tantalum capacitors for stability because their equivalent series resistance (ESR) is lowest at any temperature. The 3.3V line powers the 74HC244 octal buffer and continues on to the header to power a 3.3V flash chip.

If there are any inconsistencies or you would like to elaborate on anything above, please feel free.